A stitchless highly oriented polypropylene fabric bulk bag of the type that can hold 500 to 5000 pounds (226.7 to 2268 kilograms) of bulk material includes a highly oriented polypropylene fabric top, body and bottom, with a heat fused joint providing an airtight connection between the top and body, and another airtight heat fused joint connecting the body and bottom. A fill spout and discharge tube may also be provided with an airtight heat-fused joint connecting the fill spout to the top and another airtight heat-fused joint connecting the discharge spout to the bottom. Heat sealing machinery includes heat seal bar assemblies that can self-align during heat-sealing to apply even pressure to all areas being heat sealed. A heating element is of single-piece construction and can include end coupler portions as part of the single-piece construction. Carrier plates used in a heat-sealing assembly line guide parts placement, provide quality checks for parts placement, and tooling set-up for machinery.